NO SINGLE word in the wine universe causes more consternation, and is prone to more misuse, than the French term terroir. Terroir, as anyone who reads the back labels of wine bottles will attest, is as common as dirt. Some people think it is dirt, or the flavors that a wine picks up from dirt. Whatever it is, grape growers and winemakers all seem quite certain that it's highly desirable, and therefore they are all convinced that they have it in spades.

My own definition of terroir? It is a wine's expression — through the medium of grapes grown in a specific location — of the soil, climate, weather, elevation, latitude and orientation of that particular place. If you apply that definition in the most generous and generic way, it's pretty clear that terroir, in fact, does exist everywhere.

That does not make it desirable everywhere. Certain grapes, in certain locations, may legitimately claim to reflect the "good" terroir. In broader terms, it can be applied not only to single vineyards, but to entire regions. And though it is most often the more expensive, limited wines that give you a true expression of terroir, at times it slips into wines that are widely available.

Ravenswood's single-vineyard zinfandels have been among the most expressive when it comes to reflecting the specific character of a given vineyard. It has something to do with the flavors of old vines as well as the sites themselves. Zinfandel is an exceptionally long-lived vine, and once it has several decades of life under its trellis, certain nuances appear. Old-vine zins have more detail, and light flavors of grain and herb, rather than just blustery berry fruit. The berries are there all right, but they are a bit softer, with a plummy resonance. And the vines produce less and less with each passing decade, so the flavors, though mellow, seem more concentrated.

Ravenswood's single-vineyard designates — Dickerson, Belloni, Barricia, Big River, Teldeschi and the extraordinary Old Hill — are certainly worth hunting for. But expect to pay $35 and up for the pleasure they deliver. A more affordable glimpse of terroir is provided by the brand's County Series zins. Current releases of the Napa, Sonoma and Lodi "Old Vine" bottlings are all quite good and well-differentiated. Suggested retail is $12.

The 2010 Napa Valley Old Vine Zinfandel includes a high percentage of petite sirah in the blend, which adds dark fruits and potent tannins to the mix. It is certainly the richest, ripest tasting of the "terroir trio" — though not my personal favorite.

The 2009 Sonoma County Old Vine Zinfandel draws upon some of California's finest vines. It's given a full year and a half in French oak, about one-third new, and it definitely reflects the supple, fresh, berry-driven flavors of Sonoma.

Best of all is the 2010 Lodi Old Vine Zinfandel, my Pick of the Week.

Paul Gregutt's blog is www.paulgregutt.com. Email: paulgwine@me.com.